1. Field of the Invention
The present invention relates to a tape cartridge comprising a novel locking mechanism for locking tape hubs when not in use and more particularly to a tape cartridge wherein the locking mechanism is characterized by suspended spring members.
2. Description of the Prior Art
FIGS. 1 to 6 show an example of a conventional digital audio tape cartridge as disclosed in Japanese Patent Publication Serial No. 191102/1984.
Referring to FIGS. 1 and 2, a case body 1 is formed by combining a top half 1a and a bottom half 1b made of plastic resin material in an abutting manner using screws. There are disposed a pair of tape hubs 3 at both the left and right positions in the case body 1 for winding a recording tape 2 therearound. Both of the hubs 3 are rotatably disposed at a pair of drive shaft insertion holes 5 defined in the bottom wall 4 of the bottom half 1b of the case body 1. A pair of tape guide members 6 are provided at both right and left positions of the front portion of the case body 1. The recording tape 2 is released from one of the hubs and taken up on the other hub running along the tape guide members 6. A viewing window 11 is opened on the top wall 8 of the top half 1a so as extending in the left and right directions of the case body 1 and a transparent plate 12 is fitted in the viewing window 11 by way of ultrasonic bonding so as to cover the window 11. The window enables one to see the volume of the roll of the recording tape wound on the respective hubs.
In FIGS. 3 and 4, a pocket 7 for tape loading is defined in the front central portion of the bottom half 1b extending inward and in the left and right directions. The top portion of the pocket 7 is closed by the front part of the top wall 8 of the top half 1a with the front portion and bottom portion thereof opened.
A front lid 9 is rotatably mounted to the front face of the case body 1 for the protection of the front part of the recording tape. The front lid 9 can be rotated between a closed position to close the front portion of the case body 1 when not in use and an opened position to open the front portion of the case body when the tape cartridge is in use around a pair of supporting shafts 10. The front lid 9 is provided with the pair of supporting shafts 10 projected from side arms 9a and the supporting shafts 10 are rotatably fitted in the front portion of the side walls 13 of the case body 1.
In FIGS. 3 to 5, a shutter 14 for opening and closing the pocket 7 is slidably mounted on the outside of the bottom wall 4 of the bottom half 1b so as to move in the front and back directions of the case body 1. The shutter 14 is normally biased toward the closing position by a spring member 25.
A hub blocking plate 17 is mounted in the case body 1 for stopping the rotation of the hubs 3 when not in use. The hub blocking plate 17 is made of a plastic resin material and comprises an elongated flat plate 17a, sliding legs 17b projected downwardly from both left and right ends of the flat plate 17a, a pair of locking tips 18 projected backward from the back edge of the flat plate 17a at both left and right ends and passive projections 19 each projected from the free end of each of the sliding legs 17b. In case of mounting the hub locking plate 17 in the case body 1, a hub locking plate 17 is fitted in the gap between one of the inner surfaces of the top half 1a and a hub locking pressure plate 12a projected from the transparent plate 12, so as to slide in the front and back directions. When the top half 1a and bottom half 1b are assembled, the hub locking plate 17 can be installed in the front portion of the hubs 3 in such a manner that the hub locking plate 17 can bridge over the hubs 3 and recording tape 2, wound on the hubs 3 in the left and right directions in the bottom half 1b, and the sliding legs 17b are slidably supported on the inner face of the bottom wall 4. Thus, the hub locking plate 17, installed in the case body 1, can move between the locking position, where each locking tip 18 engages with one of the engaging teeth formed on the peripheral edge of the top of the hub, and an unlocking position where the engaging tips are disengaged from the engaging teeth and the hub locking plate 17 is normally baised toward the locking position by a spring member 22 suspended between the rib 7a projected in the left and right directions in the inner portion of the case body 1 and the flat plate 17a. Therefore, when not in use, the hub locking plate 17 makes the locking tips 18 engage with the hubs 3 to stop the hubs 3 and when the tape cartridge is loaded in a tape player, the hub locking plate 17 is moved toward the unlocking position by engagement of the passive projection 19 and the hub locking plate 17 upon opening of the front lid 9, due to the operation of the tape player.
In the digital audio tape cartridge having the conventional hub locking mechanism mentioned above, a coil spring has been used as the spring member 22 for biasing the hub locking plate 17, and the intermediate portion 22a of the spring member 22 is secured to a spring supporting member 23 formed at the intermediate position of the hub locking plate 17, and the arm portions 22b, projected from the intermediate portion 22a, resiliently abut the rib 7a. However, the way of suspending the spring member, as mentioned above, has a drawback in that the spring member 22 pushes the central portion of the hub locking plate 17 with a force F and the locking tips 18 of the hub locking plate 17 engage the hubs 3, therefore, the hub locking plate 17 is subjected to a strong bending moment, as shown in FIG. 6, whereby the hub locking plate 17 may be deformed, in particular under a hot condition, whereby the hub locking plate 17 tends to be worn away from the locking and unlocking. In the worst case only one locking tip 18 of the hub locking plate 17 will engage the hub with the other locking tip 18 being unlocked, causing incomplete locking.